This project examines the role of Helicobacter pylori (H.p.) in the gastric precancerous process. Although some of the information on such relationship is generated by project 1, it will be considered, analyzed and interpreted together with the information obtained specifically in the project. The work conducted in project 1 will concentrate on the morphologic parameters associated with H.p. that are modified with prolonged treatment (long term). This project will examine the temporal relationship between H.p. infection and histologic gastritis by means of trials with drugs which specifically control bacterial infection (bismuth, metronidazol and furazolidone) vs drugs with only cytoprotective role (sucralfate). Additionally, a case control study will address the issue of risk factor specifically associated with the type of gastritis and the complications (ulcers). Studies will be carried out in New Orleans (Charity Hospital) and Colombia, in populations at high risk of gastric cancer. Restrictions enzymes of H.p. and sensitivity to drugs will be analyzed.